Get users that made order every month from MySQL

This is my database table: orders

id	user_id	order_id	datetime
1	1	1245652	1607444387
2	2	3265784	1607357987
3	1	9521014	1607357927
4	3	1036951	1607317987

I want to have a list of users that place at least one order every month. how i can do that?

Answer

You can do something like this:

select user_id
from orders o
where datetime >= :from and datetime < :to
group by user_id
having count(distinct extract(year_month from from_unixtime(datetime))) = :num_months

:from, :to, and :num_months indicate parameters. The first two define the date range you want. The third indicates the number of months that constitute “every month” in the time frame.